2,241 research outputs found
The trion: two electrons plus one hole versus one electron plus one exciton
We first show that, for problems dealing with trions, it is totally hopeless
to use the standard many-body description in terms of electrons and holes and
its associated Feynman diagrams. We then show how, by using the description of
a trion as an electron interacting with an exciton, we can obtain the trion
absorption through far simpler diagrams, written with electrons and
\emph{excitons}. These diagrams are quite novel because, for excitons being not
exact bosons, we cannot use standard procedures designed to deal with
interacting true fermions or true bosons. A new many-body formalism is
necessary to establish the validity of these electron-exciton diagrams and to
derive their specific rules. It relies on the ``commutation technique'' we
recently developed to treat interacting close-to-bosons. This technique
generates a scattering associated to direct Coulomb processes between electrons
and excitons and a dimensionless ``scattering'' associated to electron exchange
inside the electron-exciton pairs -- this ``scattering'' being the original
part of our many-body theory. It turns out that, although exchange is crucial
to differentiate singlet from triplet trions, this ``scattering'' enters the
absorption explicitly when the photocreated electron and the initial electron
have the same spin -- \emph{i}. \emph{e}., when triplet trions are the only
ones created -- \emph{but not} when the two spins are different, although
triplet trions are also created in this case. The physical reason for this
rather surprising result will be given
Type I and type II interferon responses in two human liver cell lines (Huh-7 and HuH6)
AbstractMost studies investigating the biology of Hepatitis C virus (HCV) have used the human hepatoma cell line Huh-7 or subclones thereof, as these are the most permissive cell lines for HCV infection and replication. Other cell lines also support replication of HCV, most notably the human hepatoblastoma cell line HuH6. HCV replication in cell culture is generally highly sensitive to interferons (IFNs) and differences in the IFN-mediated inhibition of virus replication may reflect alterations in the IFN-induced antiviral response inherent to different host cells. For example, HCV replication is highly sensitive to IFN-γ treatment in Huh-7, but not in HuH6 cells. In this study, we used microarray-based gene expression profiling to compare the response of Huh-7 and HuH6 cells to stimulation with IFN-α and IFN-γ. Furthermore, we determined whether the resistance of HCV replication in HuH6 cells can be linked to differences in the expression profile of IFN-regulated genes. Although both cells lines responded to IFNs with rapid changes in gene expression, thereby demonstrating functional type I and type II signaling pathways, differences were observed for a number of genes. Raw and normalized expression data have been deposited in GEO under accession number GSE68927
A description of odd mass W-isotopes in the Interacting 2 Boson-Fermion Model
The negative and positive parity low-spin states of the even-odd Tungsten
isotopes, 183,185,187W are studied in the frame work of the Interacting
Boson-Fermion Approximation (IBFA) model. The fermion that is coupled to the
system of bosons is taken to be in the negative parity 2f_7|2, 2f_5\2, 3p_3\2,
3p_1\2 and in the positive parity 1i_13\2 single-particle orbits. The
calculated energies of low-spin energy levels of the odd isotopes are found to
agree well with the experimental data. Also B(E2) values and spectroscopic
factors for single-neutron transfer are calculated and found to be in good
agreement with experimental data
Event-, politics-, and audience-driven news: A comparison of populism in European media coverage in 2016 and 2017
This chapter focuses on trends in reporting over time. It examines the presence of populist key messages in European newspapers coverage of immigration and commentaries on current political events, at two points in time, spring 2016 and spring 2017. The chapter explores the similarities and differences in the populist content of newspapers between the two periods and identifies a set of extra-media and intra-media explanatory factors contributing to the understanding of the emerging differences in a year-to-year comparison. The findings show that the presence of populism in news and commentaries in some countries is loosely related to actual migration dynamics (see Germany and Greece), whereas in other countries it seems to follow more intensive political debates, although actual immigration is less dramatic (Bulgaria, Poland). There are fewer indications than expected that the populist tendencies in news and commentaries are a reaction to the intensity with which the population views immigration as an important national issue or is dissatisfied with decisions by political elites. Finally, there are strong indications of the great importance of intra-media factors in explaining populism in news and commentary
A realistic two-lane traffic model for highway traffic
A two-lane extension of a recently proposed cellular automaton model for
traffic flow is discussed. The analysis focuses on the reproduction of the lane
usage inversion and the density dependence of the number of lane changes. It is
shown that the single-lane dynamics can be extended to the two-lane case
without changing the basic properties of the model which are known to be in
good agreement with empirical single-vehicle data. Therefore it is possible to
reproduce various empirically observed two-lane phenomena, like the
synchronization of the lanes, without fine-tuning of the model parameters
Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence
We measured the ratio of the transverse to longitudinal
components of polarization transferred from electrons to bound protons in
by the process at the
Mainz Microtron (MAMI). We observed consistent deviations from unity of this
ratio normalized to the free-proton ratio,
, for both -
and -shell knocked out protons, even though they are embedded in averaged
local densities that differ by about a factor of two. The dependence of the
double ratio on proton virtuality is similar to the one for knocked out protons
from and , suggesting a universal behavior.
It further implies no dependence on average local nuclear density
Effect of fermionic components on trion-electron scattering
To test the validity of replacing a composite fermion by an elementary
fermion, we here calculate the transition rate from a state made of one free
electron and one trion to a similar electron-trion pair, through the time
evolution of such a pair induced by Coulomb interaction between elementary
fermions. To do it in a convenient way, we describe the trion as one electron
interacting with one exciton, and we use the tools we have developed in the new
composite-exciton many-body theory. The trion-electron scattering contains a
direct channel in which ``in'' and ``out'' trions are made with the same
fermions, and an exchange channel in which the ``in'' free electron becomes one
of the ``out'' trion components. As expected, momenta are conserved in these
two channels. The direct scattering is found to read as the bare Coulomb
potential between elementary particles multiplied by a form factor which
depends on the ``in'' and ``out'' trion relative motion indices and
, this factor reducing to in the zero momentum
transfer limit: In this direct channel, the trion at large distance reacts as
an elementary particle, its composite nature showing up for large momentum
transfer. On the contrary, the fact that the trion is not elementary does
affect the exchange channel for all momentum transfers. We thus conclude that a
3-component fermion behaves as an elementary fermion for direct processes in
the small momentum transfer limit only
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